INTRODUCTIONrnOsteoporosis is a disease defined by low bone density and disruption of the bone architecture resulting in fragility and fractures.1 Hereditary forms of bone fragility called osteogenesis imperfecta (OI) or“brittle bone disease”are mostly linked to dysregulation of Type I collagen.2 Approximately 90％of OI cases stem from mutations in collagen I genes,3–4 while most of the remaining forms affect collagen-processing enzymes involved in collagen folding, posttranslational modifications, intracellular transport, or matrix incorporation.